Hydraulic pump



April 9- R. H. SHEPARD 2,467,916

HYDRAULIC PUMP Filed Sept. 6, 1946 6 Sheet s-Sheet 1 INVENTOR RALPH/i 51mm 25 34- I BY wo w April 1949- R. H. SHEPARD I 2,467,916

HYDRAULIC PUMP Filed Sept. 1946 6 Shets-Sheet 3 INVENTOR RALPH H. SHEPARD mi/mm ATTORNEY April 1 R. H; SHEPARD 2,467,916

HYDRAULIC PUMP Filed Sept. 6, 1946 6 SheetsSheet 4 A all,

INVENTOR RALPH HJHEPARD ATTORNEY ma /MM,

April 19, 1949. R. H. SHEPARD HYDRAULIC PUMP Filed Sept. 6, 1946 6 Sheets-Sheet 5 INVENTQ R RALPH H. JHEPARD I Mai/mm,

ATTORNEY R. H. SHEPARD nmmuuc PUMP April 19, 1949.

Filed Sept. 6, 1946 6 Sheets-Sheet '6 INVENTOR RALPH H. 5HB4RD WWW ATTORNEY Patented Apr. 19, 1949 Ralph n. Shepard, New .York, N. Y., Nathan Manufacturing Company,

assignor to New York,

' N. Y., a corporation of- New York Application September 6, 1946, Serial No. 695,125

' in its reciprocation, the amplitude of which is a factor of the lateral displacement of the fixed pivot. Manual means are provided for adjusting the lateral displacement of each fixed pivot.

Application for patent, Serial No. 624,552 now Patent No. 2,430,394, granted Nov. 4, 1947, of

11 Claims. C1. 103-4) which I am one of the joint'inventors, discloses I certain improvements in the patented pump. In accordance with the invention of that application all of the fixed pivots are mounted on a common movable member so that a single adjustment suflices for all, and means are provided, controlled by the discharge pressure of the pump, for

automatically adjusting the lateral displacementof the fixed pivot or pivots to vary the piston stroke and thereby maintain a constant discharge pressure.

This present invention is a carrying forward of the improvements disclosed in application for patent, Serial No. 624,552. Thus, I have here provided in the pump a source of secondary fluid pressure for adjusting the lateral displacement of the fixed pivots to vary the piston strokes which in turn is controlled by the discharge pressure of the pump, and also optional means to make up automatically any loss in the pressure fluid from the fluid handled by the pump. The source of this secondary fluid pressure is preferably a secondary or regulating pump, similar in construction and operation to the primary pump except that it is reversible, the pressure of which adjusts the common movable member on which the primary fixed pivots are mounted, the piston stroke of the secondary pump being itself adjustable in response to the dischargepressure of the primary pump. The adjusting fluid operates against a working pressure only when required to change the adjustment. Other novel features will become apparent in the following specification.

In the drawings which illustrate a preferred embodiment of the invention,

Fig. 1 is a plan view of the pump assembly;

Fig. 2 is a left hand side view of the same showing in dotted lines certain passages important in the mechanism; a

Fig. 3 is a longitudinal sectional view of the same along the plane of line 3-3 in Fi 1;

Fig. 4 is a fragmentary sectional view along the plane of line 4-4 in Fig.2;

Fig. 5 is a fragmentary sectional view along the planes of'line 5-5 in Fig. 2;

Fig fi is a cross sectional view, its left half along the plane of line Sa-Ga in Fig. 3, and its right half along the plane of line 6b6b in Fig. 3;

Fig. '7 is a cross sectional view, its left half along the plane of line lat-la in Fig. 3, and its right half along the plane of line lb-11) in Fig. 3;

Fig. 8 is a fragmentary sectional view along the plane of line 8-8 in Fig. 7;

Fig. 9 'is a cross sectional view along the plane of line 9-9 in Fig. 3;

Fig. 10 is across sectional view, its left half along the plane of line loaf-Illa in Fig.3, and its right half along the plane of line llibl6b in Fi 3;

Fig. 11 is a cross sectional view along the plane of lineH-H in Fig. 3;

Fig. 12 is adiagrammatic view of the primary and secondary pump pistons in no-stroke or minimum positions, as shown in Fig. 11;

Fig. 13 is a cross sectional view, partly diagrammatic, similar to Fig. 11, but showing the mechanism in the initial position which it assumes when the discharge pressure of the pump is decreased;

Fig. 14 is a diagrammatic view of the mechanism conforming to Fig. 13;

Fig. 15 is a cross sectional view, partly diagrammatic, similar to Fig. 13, but showing the mechanism with the primary pump pistons operating at fullstroke to reestablish the .full discharge anism conforming to Fig. 17.

Like characters of reference denote similar parts throughout the various views and the following specification. J, v

The primary pump illustrated is housed with in a casing comprising a pump cylinder block 2i, a manifold 22, a body 23and a base 2 3. The manifold 22 is provided with an inlet 25 supplying liquid through inlet passage 26, and passages 21, 28, 29 and 30 in thepump cylinder block 2| to annularly disposed cylinders 3|, with a piston 32. Each piston 32 has an elongated transverse duct 33 connected with a longitudinal duct-34 in communication-with the end of its cylinder and each is rotated and reciprocated in its cylinder in the manner described in U. S.

each fitted shaft 4| supported in a bearing sleeve 42 forming part of the base 24. The crank shaft 4| is 7 provided with a crank pin 43 on which a disk 44 is mounted. A counterbalance weight 45 is secured by means of a key 45 to an extension 41 of the crank pin 43. The crank shaft 4| is held in longitudinal alinement by means of a shoulder 48 on crank shaft 4| and a thrust face 49.

The crank shaft 4| is provided at its outer end with an oil seal 50 to prevent leakage of fluid around the end of the shaft.

By referring to Fig. 3, it will be noted that the disk 44 is provided with a number of spaced circular openings which serve as bearings for ofi-set extensions or crank pins 52 of the pistons 32. The crank pins 52 are eccentrically located with respect to the pistons 32, and the eccentricity with respect to the pistons 32 is the same as the eccentricity of the crank pin 43 with respect to the crank shaft 4|. Rotation of the crank shaft 4| therefore results in corresponding rotation of the pistons 32.

The outer end of crank pin 52 of each piston 82 is provided with a socket 53 which receives one ball 54 of a ball link 55 and serves as a pivot therefor. The ball 54 is movably secured in the socket 53 by means of a retainer 55. The retainer 58 is locked in place, by suitable means (not shown). The ball link 55 is provided at its other end with a ball 51 likewise secured in a socket 58 of a regulating disk 59 by means of a retainer 50, the socket 58 serving as a fixed pivot for the link 55. The regulating disk 59 is rotatably supported on the bearing sleeve 42 and is provided with a pin 5|.

Reference to Fig. 11 shows in the base 24, at substantially right angles to the longitudinal axis of the pump. plungers 62 and 53 slidingly fitted within cylinders 54 and 55, respectively. Caps 55 serve to close cylinders 54 and 55. Pin 5| projects into the base 24 so as to ,be-disposed between opposite inner ends of alined plungers 52 and 53.

51 and 58 are semi-circular grooves in the inner bore of body 23 forming annular ducts between the body 23 and pump cylinder block 2|. 59 are the cylinders of the secondary pump, annularly disposed in the body 23 and of somewhat smaller diameter than cylinders 3| in block 2|. Each cylinder 59 communicates with duct 51 by an oblique passage. and by a straight passage 1| with duct 58. The passages 10 and 1| terminate in each cylinder at opposite walls and in the same plane. Each cylinder 59 is fitted with a piston 12 having an elongated transverse duct 13 con-' nected with a longitudinal duct 14 in communication with the end of its cylinder and each is rotated and reciprocated as described later causing duct 13 to communicate alternately with passages and 1| and their connecting grooves.

51 and 58.

Crank shaft 4| is provided with an eccentric 15 intermediate its shoulder 48 and crank pin 43. A disk 15 is mounted on eccentric 15 and is provided with a number of spaced circular openings 11 which serve as bearings for offset extensions or crank pins 18 of the pistons 12. The crank pins 18 are eccentrically located with respect to the pistons 12, and the eccentricity with respect to the pistons 12 is the same as the eccentricity of eccentric 15. Rotation of the crank shaft 4|, and particularly the eccentric 15,

5 therefore results in corresponding rotation of the pistons 12.

The outer end of crank pin 18 of each piston 12 is provided with a socket 19 which receives one ball 85' of a ball link 8| and serves as a pivot 10 therefor. The ball 88 is movably secured in the socket 19 by means of a retainer 82. The ball 7 link 8| is provided at its other end with a ball 83 likewise secured in a socket 84 of an adjusting disk 85 by means of a retainer 85, the socket 84 serving as a fixed pivot for the link 8|. The

adjusting disk 85 is rotatably supported on the base 24 and bearing sleeve 42 and is provided with a pin 81. Disk 85 is further provided with an arcuate slot 88 to clear pin 5| which projects go through it in its various positions. Disk 16 has a number of similar slots 89 to clear ball links 55 projecting through it.

In the base 24, in substantially the same horizontal plane as plungers 52 and 53 but at the g5 opposite side of the crank shaft 4|. is a small piston 90 slidablydisposed within a cylinder 9|. A cap 92 closes an open end of the cylinder 9|. Pin 81 is held in contact with an inner end of piston 98 by a spring 93 and a spring container or follower 94, preferably coaxially disposed with piston 90. A cap 95 serves as a stop for spring 93 and, being adjustable. regulates the tension of the spring.'which in'turn determines the discharge pressure, asI shall explain presently.

A duct 95 from the outlet in the manifold 22 runs through-cylinder block 2|. body 23 and into base 24 to a transverse duct 91, one end of which communicates with the outer end of cylinder 9|, while its other end communicates with the side wall of cylinder 64 and a branch 98 of duct 91 communicates with the side wall of cylinder 55. Annular groove 51 by way of an oblique duct 99 and longitudinal duct I08 communicates with the outer end of cylinder 54, while annular groove 58 by way of a'straight duct Ill and longitudinal duct I02 and transverse duct I03 communicates with the outer end of cylinder 55.

Referring now to Fig. 12, it will be noted that when the. regulating disk 59 is turned into a position where the ball terminal 51 of the link is in line with the center of piston 32, the rotation of the piston 32 as imparted to it by the disk 59, does not result in any reciprocating movement of the piston. 0n the other hand, referring to Fig. 16, it will be noted that when the disk 59 has been rotated a certain angle so that ball terminal 51 of the link 55 which serves as a universal coupling has been displaced a distance A'from the center line of the piston 32,

The regulating disk 59 is turned by pressure exerted by plungers 52 and 53 against pin 5|, as will be explained later.

Pistons 12 are rotated and reciprocated by eccentric 15, disk 15, ball link 8| in cooperation with adjusting disk 55, in a manner substantially the same as previously explained in reference to pistons 32, the disk being turned by pressure the piston will be reciprocated while it is being exerted by piston 90 and spring 93, as will be explained presently.

In assembling the pump, fluid is admitted into grooves 61 and 68, ducts 99, I00, NH, I02, )3, cylinders 64 and 65 which form substantially a closed system. If preferred, additional caps 66 may be'provided to inject a fluid into this system after assembling and prevent air from being trapped in the system. I

In Fig. 11, and in the diagram of Fig. 12, the pump is shown with both the primary pistons 32 and the secondary pistons 12 at no-stroke position when there is pressure is prevalent. In this position the operating pressure admittedthrough ducts 96 and 91 against one end of piston 90 is balanced by the force of spring 93 and pin 81 is in a no-stroke position, as shown in Fig. 12. Inasmuch as pin 81 is in a no-stroke position and pistons 12 do not operate, no fluid is pumped into or withdrawn from cylinders 64 and 65, and plungers.

62 and 63 remain in whatever position they may be which, as illustrated, is that in which the pin 6| is also in a no-stroke position. Lateral displacement of the fixed pivots of either pump is necessary to its pumping .action. When eitherthe primary or secondary pistons are in no-stroke position, the lateral displacement of their fixed pivots is zero.

If the pressure in the hydraulic line should drop due to operating certain mechanisms-the pressure in ducts 96and 91, which are in direct communicationwith the outlet of the pump in the manifold, decreases correspondingly. The

greater force of the spring 93 then moves pin 81 toward the left, as indicated in Fig. 13,-which causes the adjusting disk 85, to turn, the pistons 12 to reciprocate as well as rotate and to transfer fluid from the outer end of the cylinder 65 to the outer end of the cylinder '68, thereby causing the pin iii to assume the position indicated in Fig. 15. The pin Bl has then turned regulatto continuous pumping action and no operation of mechanisms, the increase in pressure forces pin 81 to the right against the force .of the spring 93 as shown in Figs. 1'? and 18 which causes the fluid from the outer end of plunger 62 to be transferred to the outer end of plunger 63 until-the conditions are equalized and the primary and secondary pistons again assume no-stroke posi-' tions.

Attention is particularly drawn to the fact that the pistons 12 and their cooperating ducts I9 and." are so disposed that the pistons will pump in either direction so that the flow of fluid in the closed system is reversible. Suppose, for example, under the conditions of Fig. 14, one of the pistons 12 is rotating from the position indicated by broken lines to that indicated by solid lines. During this period the piston is beingv withdrawn from its cylinder 69. If the ducts 13 and 14 in this piston communicate with ducts ll, 68, I02 and H13 inthe body and base at this time,fiuid no consumption of fluid in the hydraulic'line and the des'irednormal operating will be'withdrawn throughthe latter and from the outerend of piston 63. Now suppose the conditions are-changed so the pivot through the body and base 83 is shifted to the opposite side of its no-stroke position, as in Fig. 18, and a piston "is again rotating in the same direction from theposltion shown by broken lines to that shown by solid lines. During this period the piston is now being drivenint'o its cylinder 69 and, if the ducts I3 and I4 in the piston communicate with ducts H, 68, I02 and I03 as before,

ducts against the outer end of piston 63. Thus, by shifting the pivot 83 to the other side'of its no-stroke posi-* tion, the longtiudinal movement of the piston is reversed during a given period of its rotation. In this manner, suction strokes are changed to delivery strokes and vice through direction.

Anyslight loss of the fluid in the closed system.

be made up by slight leakagewill automatically from ducts 91 and in cylinders 64 and 98 past plungers 62 and 63 65, .respectively, provided the same fluid is used in the pump and the closed system.

It is clearly evident that the secondary pistons 12 do not operate continuously against pressure, but operate only when necessary to transfer fluid in the closed system to adjust the strokes of the pumping pistons 32; furthermore, the pressure in the closed system need not be the same or as high as the pressure in the hydraulic line but need only be suflicient to operate this transfer.

While I have shown ducts 96 and 91, in communication with the outlet of the pump, permit fluctuations in pressure to be imparted to the piston 80 and so adjust by .pin 81 the position of the disk 85, these ducts may be omitted and other means, entirely independent of the pump.

pressure, may be used for this purpose, such as thermostatic means, or other means responsive to operating variations.

The positions of the pins 81 and Si and their associated parts are shown in their extreme positions in Figs. 13 through 18, but this isfoi illustrative purposes only. Actually, the movements would be much smaller. Thus, the moment the discharge pressure falls, spring 93 shifts the pin 81, which immediately causes the secondary pump to shift pin 6!, which in turn starts the primary pump to bring back the discharge pressure to the predetermined point. But this pressure will overshoot the mark if the primary pump continues to operate, and this in its turn shifts pin 81", compresses spring pivots of the secondary pump to of alinement. with their piston axes, thereby reversing the action of the secondary pump, which tends to return pin iii to its no-stroke position. When a pump of this character is used to maintain a'constant pressure in a system from which various mechanisms are operated, the nostroke position is the norm to which both primary and'secondary pistons are automatically returned. However, if the pump were constantly delivering fluid at a constant pressure, the norm for the primary pistons would be some other position and the length of stroke of the primary pistons would vary above and below that necessary to maintain the given discharge pressure, never reaching the no-stroke position.

Many changes in the form, proportion, combination of parts and minor details of construction may be resorted to without departing from the principles or sacrificing any of the advantages of the invention, as defined in the appended fluid will be forcedv versa, and fluid flows. the closed system in the opposite 93 and moves the fixed the other side 7 WhatIclaimasnew,is: 1. A pump comprising a cylinder having inlet and discharge passages, a rotary and reciprocatory piston in the cylinder having means for alternately placing the inlet and discharge passages in communication with the cylinder as the piston rotates, an eccentric pivot carried by the piston, a fixed pivot laterally displaced with reference to the piston axis, a universal coupling between the pivots, means for rotating and thereby reciprocating the piston, a source of secondary V fluid pressure for adjusting the lateral displace ment of the fixed pivot to regulate the stroke of the piston, and means controlled by the discharge pressure of the pump for controlling the secondary fluid pressur i 2. A pump comprising a cylinder having inlet 7 and discharge passages, a rotary and reciprocatory piston in the cylinder having means for alternately placing the inlet and discharge passages in communication with the cylinder as the piston rotates, an eccentric pivot carried by the piston, a fixed pivot laterally displaced with reference to the piston axis, a universal coupling between the pivots, means for rotating and thereby reciprocating the piston, a source of secondary fluid pressure for automatically adjusting .the lateral displacement of the fixed pivot to regulate the stroke of the piston, and means controlled by the discharge pressure of the pump for automatically controlling the secondary fluid pressure.

3. A pump comprising a cylinder having inlet and discharge passages, a rotary and reciprocatory piston in the cylinder having means for alternately placing the inlet and discharge passages in communication with the cylinder as the piston rotates, an eccentric pivot carried by the piston, a fixed pivot laterally displaced with reference to the piston axis, a universal coupling between the pivots, means for rotating and thereby reciprocating the piston, a source of secondary fluid pressure for adjusting the lateral displacement of the fixed pivotto regulate the stroke of the piston, means controlled by the discharge pressure of the pump for controlling the secondary fluid pressure, and means for making up any loss in the secondary pressure fluid from the fluid handled by the pump.

4. A pump comprising a cylinder having inlet and discharge passages, a rotary and reciprocatory piston in the cylinder having means for al-'- ternately placing the inlet and discharge passages in communication with the cylinder as the piston rotates, an eccentric pivot carried by the piston, a fixed pivot laterally displaced with reference to the piston axis, a universal coupling between the pivots, means for rotating and thereby reciprocating the piston, a secondary pump for creating a fluid pressure for adjusting the lateral displacement of the fixed pivot to regulate the stroke of the piston, and means controlled by the discharge pressure of the primary pump for regulating the discharge of the secondary pump.

5. A pump comprising a cylinder having inlet and discharge passages, a rotary and reciprocatory piston in the cylinder having means for alternately placing the inlet and discharge passages in communication with the cylinder as the piston rotates, an eccentric pivot carried by the,

piston, a fixed pivot laterally displaced with reference to the piston axis, a universal coupling between the pivots, means for rotating and thereby reciprocating the piston, a reversible secondary pump for creating a fluid pressure for adjusting the lateral displacement of the fixed pivot to regulate the stroke 01' the piston, and

means controlled by the discharge pressure of the primary pump for regulating the discharge of the secondary pump.

6. A pump comprising a cylinder having inlet and discharge passages, a rotary and reciprocatory piston in the cylinder having means for alternately placing the inlet and discharge passages in communication with the cylinder as the piston rotates, an eccentric pivot. carried by the piston, a fixed pivot laterally displaced with reference to the piston axis, a universal coupling between the pivots, means for rotating and thereby reciprocating the piston, a secondary pump for creating a fluid pressure, the secondary pump comprising a cylinder having inlet and discharge passages, a rotary and reciprocatory piston in the cylinder having means for alternately placing the inlet and discharge passages in communication with the cylinder as the piston rotates, an eccentric pivot carried by the piston, a fixed pivot laterally displaced with reference to the piston axis,,a universal coupling between the pivots, and means for rotating and thereby reciprocating the piston, means controlled by the discharge pressure of the primary pump for adjusting the lateral displacement of the fixed pivot of the secondary pump to regulate the stroke of its pis- Piston s, an eccentric pivot carried by the piston, a fixed pivot laterally displaced with reference to the piston axis, a universal coupling between the pivots, means for rotating and thereby reciprocating the piston, a reversible secondary pump for creating a fluid pressure, the secondary pump comprising a cylinder having inlet and discharge passages, a rotary and reciprocatory piston in the cylinder having means for alternatingly placing the inlet and discharge passages in communication with the cylinder as the piston rotates, an eccentric pivot carried by the piston, a fixed pivot laterally displaced with reference to the piston axis, a universal coupling between the pivots, and means for rotating and thereby reciprocating the piston, means controlled by the discharge pressure of the primary pump for adjusting the lateral displacement of the fixed pivot of the secondary pump to either side of alinement with its piston axis and thus regulate the stroke of its piston and determine the amount and direction of thefiuid pressure created, and means controlled by the pressure of the secondary pump for adjusting the lateral displacement of the fixed pivot of the primary pump to regulate the stroke of the piston of the primary D mp.

8. A pump comprising a casing having an inlet and an outlet, a plurality of cylinders, each cylinder having an inlet passage in communication with the inlet and a discharge passage in communication with the outlet, a rotary and reciprocatory piston in each cylinder having means for alternately placing said inlet passage and said discharge Passage in communication with the cylinder as the piston rotates, an eccentric pivot carried by each piston, a fixed pivot for each piston laterally displaced with reference to the'piston axis, a universal coupling between each fixed and eccentric pivot, means for rotating and thereby reciprocating the fluid pressure for simultaneously adjusting the lateral displacement of all the fixed pivots to regulate the stroke of the pistons, and means controlled by the discharge pressure Of the pump for controlling the secondary fluid pressure.

9. A pump comprising a casing having an inlet and an outlet, a plurality of cylinders, each cylinder having an inlet passage in communication with the inlet and a discharge passage in communication with the outlet, a rotary and reciprocatory piston in each cylinder having means for alternately placing said inlet passage and said discharge passage in communication with the cylinder as the piston rotates, an eccentric pivot carried by each piston, laterally displaced with reference to the piston axis, a universal coupling between each fixed and eccentric pivot, means for rotating and thereby reciprocating the pistons, a secondary pump for creating a fluid pressure for simultaneously adjusting the lateral displacement of, all the fixed pivots to regulate the stroke of the pistons, and means controlled by the discharge pressure of the primary pump for regulating the operation of the secondary pump.

10. A pump comprising a casing having an inlet and an outlet, a plurality of annularly arranged cylinders, each cylinder having an inlet passage in communication with the inlet and a discharge passage in communication with the outlet, a rotary and reciprocatory piston-in each cylinder having means for alternately placing the inlet and discharge passages in communication with the cylinder as the piston rotates, an eccentric pivot carried by each piston, a rotary disk, a

plurality of annularly arranged fixed pivots on the disk corresponding in number to the cylinders, a universal coupling between each eccentric pivot and a fixed pivot, means for rotating and thereby reciprocating the pistons, a secondary pump for creating a fluid pressure, the secondary pump comprising a plurality of annularly arranged cylinders, each cylinder having inlet, and discharge passages, a rotary and reclprocatory piston in each cylinder nately placing the inlet and discharge passages in communication with the cylinder as the piston rotates, an eccentric pivot carried by each piston. a rotary disk, a plurality of annularly, arranged fixed pivots on the to the cylinders, a universal coupling between each eccentric pivot and for rotating and thus reciprocating the pistons, means controlled by the discharge pressure or the pistons, a source of secondary a fixed pivot for each piston having means for alterdisk corresponding in number a fixed pivot, and means primary pump'ror automatically turning the disk of the secondary pump to adjust the lateral displacement of the fixed pivots of the secondary pump with reference to their corresponding piston axes and thus regulate the stroke of its pistons and determine the fluid pressure created, and means controlled by the pressure or the secondary pump for turning the disk or the primary pump to adjust the lateral displacement of the secondary pump to either fixed pivots of the primary pump with reference to their corresponding piston axes and thus regulate the stroke of the pistons and maintain a constant discharge pressure.

11. A pump comprising a casing having an inlet and an outlet, a plurality of annularly arranged cylinders, each cylinder having an inlet passage in communication with the inlet and a discharge passage in communication withthe outlet, a rotary and reciproca-tory piston in each cylinder having means for alternately placing the inlet and discharge passages in communication with the cylinder as the piston rotates, an eccentric pivot carried by each piston, a rotary disk, a plurality of annularly arranged fixed pivots on the disk corresponding in number to the cylinders, a universal coupling between each eccentric pivot and a fixed pivot, means for rotating and thereby reciprocating the pistons, a reversible secondary pump for creating a fluid pressure, the secondary pump comprising a plurality of annularly arranged cylinders, each cylinder having in- 1 let, and discharge passages, a rotary and reciprocatory piston in each cylinder having means for alternately placing the inlet and discharge passages in communication with the cylinder as the piston rotates, an eccentric pivot carried by each piston, a rotary disk, a plurality of annularly arranged fixed pivots on the disk corresponding in number to the cylinders, a universal coupling between each eccentric pivot and a fixed pivot, and means for rotating and thus reciprocating the pistons, means controlled by the discharge pressure of the primary pump for automatically turning the disk or the secondary pump to adjust the lateral displacement of the fixed pivots or the side of allnement with their corresponding piston axes and thus regulate the stroke of its pistons and determine the amount. and direction of the fluid pressure created, and means controlled by the pressure of the secondary pump for turning the disk or the primary pum to adjust the lateral displacement of the fixed pivots or the primary pump with reference to their corresponding piston axes and thus.

regulate the stroke of the pistons and maintain a constant discharge pressure.

- RALPH H.- SHEPARD.

No references cited. 

